Rotor blading for rotary engines, particularly for steam turbines and gas turbines



1,639,247 A. ZOELLY ET AL v ROTARY ENGINES, PARTICULARLY Fon BINEs AND GAS TURBINES Aug. 16, 1927.

4RoToR BLADING FOR STEAM TUR Filed May 27. 1926 Patented ug. 16, 1927.

narran- STA ALFRED'ZOELLY AND SPIESS, OF ZURICH,

TEsfrATENT OFFICE..

SWITZERLAND.

GAS TURBINES.

Appleationled May 27, 192.6, Serial No.

rlhis invention relates to ka `rotor blading tor rotary .engines andk steam turbines and gas turbines.- vlt is known that under certain conditions with such "bladings dangerous stresses vlin the blades and in the shroudings may occur on account of natural vibrations of the blades. Such natural vibrations have repeatedly been the cause ot. violent` destructions. ln order to obviate this danger the blading according to the present invention comprises at least two terms ot bladesr having difierentV frequencies of natural vibrationwhereby the blades ot different lfrequencies oit natural vibration disturb each other so that a resultant trequency ot the natural vibration of the blading is. obtained, which, at practicallyT normal speed ot theengine, has no longer any dangerous effect Jon the strength ot the blades. l

Constructional examples ot the subjectv matter ot the present invention are illustrated on the accompanying drawings in which: i y

i 'D'. l is a section along line I-l in Fig. 2 through a )ortion ot a rotor blade rim having two dilierent forms of blades.

l is a radial section along line lal in Figs 2,

F 2 in a plan view ot Fig. l,

F is a section along line Illlll in Fig. ithrough a rotor blade rim in which gro-.ips consisting ot two blades having one determined torni alternate with groups consisting ot two blades having a second torni,

l is a plan-view ot Fig. 3.

5 is a section along line V-V in Fig. 6, through a blade rim with which gro-ups ot blades ot' different shape and having weak shrouding alternate with groups of blades ot different shape and having a strong shrouding.

Fig. is a plan view ot Fig. 5.

Figs.V and 8 are sect-ions through blade ri ius with modified groups or" blades.

rlhe rotor blading illustrated in Figs. l, 1 and Q comprises blades l having a large taper and blades 2 having a small taper. The blades l are provided with a weak shrouding 3 and 'the blades 2 with a strong shrouding l. As is shown in the drawings the blades l having a large taper and a weak shrouding 8 alternate in the blading with the blades 2 having a small taper and particularly for 112,097, ma in switzerland nay 2s, 12525.

a strong shrouding l. TheV shrouding ot one form of. .blades interengages Vthe adjacent shrouding of the other form Vof blades by means ot a spigot 5 on one shrouding entering a notch 6 on the adjacent shrouding (Fig. 2). The blades l and 2 have vthus different frequencies of natural vibration. The tact that the shrouding of adjacent blades l and 2 `interengage by means ot a spigot and notch causes these blades to disturb each other so that a resultantreque/ncy of natural vibrations of the blading is obtained which, at practically normal .speed ot the engine, has no longer any dangerous effect on the strength of the blading.l rThe 4tacings 7 (see Fig. 2) cause' the disturbingor" the natural ,vibrations ot the blades l and 2 which occur in they circumferential direction ot the rotor blade rim, whilst the'tacings S disturb 'the natural Vibrations of the bladesl and 2 occurring in the direction at right angles to the circumference of 'the rotor blade rim. i' y With the arrangement illustratedin Figs. 3 and 4 groups consisting of two blades 'l having a large taperand a weak shrouding 3 alternate with groups ot two blades Z having a smallV taper and a strong shrouding 4t. The shroudings 3 and 4; respectively interengage also in this case by means of spigot 5 and notch 6.

The groups of blades arranged circumterentially one after the other may comprise anyfnumber of blades having the saine trequency of natural vibrations. Y

As is shown in Figs. 5 and 6 every group having a strong shrouding fl as well as every group having a weak shrouding 3 may be composed of a number ot blades l having a large taper and of a number otblades 2 having a small taper.

As is shown in Fig. 7 groups comprising at least two blades 1 having a large taper and a weak shrouding 3 may alternate with only one blade 2 having a small taper and a strong shrouding 4 or, as is shown in Fig. 8, only one blade l having a large taper and a weak shrouding may alternatewith a group comprising at least two blades 2 having a small taper and a strongshrouding 4.

Finally it may be mentioned that it` is within the scope of the invention to obtain the mutual disturbing of the different 'trequenoies ot natural vibrations also in another manner than by means of a spigot itl-0 of one shrouding engaging a notch of the adjacent shrouding.

It will, of course, be obvious that the disturbing or interfering frequencies of two blades or groups of blades or a single blade and a group of .blades will produce in them resulting frequencies of vibration that are less tha-n their natural frequencies of vibration. Y

Ve claim:

1. Rotor blading for rotary engines, particularly for steam and gas'turbines, comprising at least two forms of blades having different frequencies of natural vibration and means to produce a resultant frequency of the blades which at practically normal speeds has no dangerous effect on the blading.

2. A rotor blading for rotary engines and particularly for steam-turbines and gasturbines, comprising blades having a large taper, blades having a small taper alternately arranged with blades having a large taper, a weak shrouding connected to the blades having a large taper, a strong shrouding connected to the blades having small taper, and an interconnection between adjacent shroudings.

3. A rotor blading for rotary engines and particularly for steam-turbines and gas-turbines, comprising groups of two blades havino' a large taper, groups of two blades having a small taper alternately arranged with the groups of blades having a large taper, weak shroudings connecting the blades of the groups of blades having a large taper, strong shroudings connecting the blades of the groups of blades having a small taper, and an interconnection between adjacent shroudings.

l. A rotor blading, for rotary engines and particularly for steam-turbines and gas-turbines, comprising groups of two blades having a" large taper, groups of two blades havthe groups of blades hav-ing ing a small taper alternately arranged with the groups of blades having a large taper, weak shroudings connecting the blades of a large taper, strong shroudings connecting the blades of the .groups ofblades having a vsmall taper,V

and a spigot on one shrouding engaging a notch on the adjacent shrcuding.

5. A rotor blading for rotary engines and particularly for steam-turbines and gas-turbines, comprising at least two forms of blades having different frequencies of natural vibration Ywith engaging shroudings connected to the blades, the shrouding connected to one form of blades being different in thickness from the shrouding connected to the other form of' blades, said sh-roud'ings causing the blades of different frequencies of natural vibration to disturb each other.

6.` The art of counteracting the dangerous effect of vibration of rotor blad-es of gas and steam turbines, which comprises forming the blades with interfering vibration frequencies, assembling the blades to combine such frequencies into resultant vibration frequencies less than the natural frequencies of the respective blades 'and which have no deleterious elfectupon the blades.

7. The art of counteract-ing the dangerous effect of Vif'ibration of rotor blades of gas and steam turbines, whichcompri-ses forming the blades with interfering vibration frequencies, assembling the blades to combine sucli frequencies into resultant vibration frequencies less than the natural vibration frequency of the respective blades and of less amplitude than the natural amplitude of the blades so that no deleterious effect will be produced upon the blades.

In testimony whereof, we have signed our names to this specification.

ALFRED ZOELLY. PAUL SPIESS. 

